The invention relates to an apparatus and a method for transporting a radioactive source into and out of an enclosure.
Radioactive materials are used in many fields, such as energy development, hydrocarbon exploration, and medical and scientific research. In hydrocarbon exploration, the radioactive source is located inside a carrier disposed within a downhole tool, such as a wireline logging, measurements-while-drilling (MWD), or logging-while-drilling (LWD) tool, and the downhole tool is passed through a borehole penetrating a geological formation of interest. One conventional technique involves irradiating the formation with high-energy neutrons and monitoring the resulting energy spectra, which are generally indicative of the characteristics of the formation. The radioactive source carrier is secured in a radiation carrying shield when it is not inside the downhole tool. A dedicated handling tool is used to transfer the radioactive source carrier between the radiation carrying shield and the downhole tool. It is desirable that such handling tools allow for efficient and safe handling of the radioactive source carrier in order to minimize exposure time to the radioactive source, prevent any unintended release from the radioactive source, and maximize the distance between the radioactive source and the tool operator.
Handling tools for transporting radioactive source carriers into and out of enclosures such as downhole tools and radiation carrying shields are known in the art. One prior art handling tool has several finger-shaped members at a terminal end that are adapted to close around a dovetail on a cap of the radioactive source carrier. The finger-shaped members are closed around the dovetail by rotating the tool. Often, the finger-shaped members do not securely grasp the dovetail, for example, because they are worn, rusty, broken, bent, too short, dirty or frozen, making it easy for the radioactive source carrier to become loose during transport. A secondary locking feature includes a wire spring clip on a loose chain secured to the side of the tool. The operator squeezes the spring clip while inserting the wire part of the clip into a mating hole in the cap of the radioactive source carrier. Securing the wire part of the clip to the cap requires the operator, while holding onto the handling tool, to reach very close to the carrier. Other handling tools are described in, for example, U.S. Pat. No. 5,126,564 (Perry et al.) and U.S. Pat. No. 4,845,359 (Wraight).